Boris Johnson warns against Brexit 'betrayal'

British Foreign Secretary Boris Johnson will on Wednesday use a major speech to warn that attempts to frustrate Brexit would lead to "ineradicable feelings of betrayal".

Johnson, who was one of leading campaigners behind Brexit, will also urge those who voted to leave the European Union to make peace with those who wanted to stay in the bloc, with the issue still the cause of deep divisions in British society.

During the London speech, the first of series of high-profile ministerial addresses on leaving the EU, he will urge Brexiteers to "reach out to those who still have anxieties.

"It is not good enough to say to Remainers -- you lost, get over it; because we must accept that many are actuated by entirely noble sentiments, a real sense of solidarity with our European neighbours and a desire for the UK to succeed," he will say, according to extracts released by the foreign ministry.

Johnson will, however, also fall back on phrases often used by the pro-Brexit side, accusing some people of attempting to "frustrate the will of the people" and stop Britain leaving the EU.

"I believe that would be a disastrous mistake that would lead to permanent and ineradicable feelings of betrayal. We cannot and will not let it happen," he will say.

The foreign minister's previous interventions have often put him at odds with fellow ministers, who have accused him of sowing internal division and undermining Prime Minister Theresa May.

But Wednesday's speech kicks off a series of coordinated ministerial addresses, which will include one by May on Saturday.

- 'Intolerable, undemocratic' -

Three other key cabinet ministers will follow over the subsequent two weeks, after which May will make a second address to the nation.

Setting the stage for his London speech, Johnson wrote a column in popular tabloid The Sun, in which he denied claims that Brexit represented a retreat from the world.

"The exact reverse is true," he wrote. "We are becoming every year more global."

But he said that "we also need to ask ourselves some hard questions about the impact of 20 years of uncontrolled immigration by low-skilled, low-wage workers".

He also insisted that Britain had to leave the customs union in order to strike free-trade deals with the rest of the world.

"It is only by taking back control of our laws that UK firms and entrepreneurs will have the freedom to innovate, without the risk of having to comply with some directive devised by Brussels," he wrote.

"That would be intolerable, undemocratic".

Johnson's upcoming address was described as "hypocrisy of the highest order" by opposition lawmaker Chuka Umunna.

"Boris Johnson is totally unqualified to preach about the perils of fear and betrayal when he engaged in disgraceful scaremongering" during the referendum campaign, the lawmaker said in a statement issued by the pro-EU campaign group Open Britain.